Effect of Magnetic Field for Sustaining Low Current DC Vacuum Arcs

Effects of the magnetic field on sustainment and dynamics of low current DC vacuum arcs, less than 30A, were examined. Arcs were ignited by the opening of butt contacts made of zinc. Without magnetic field, the cathode spot moves at random on the cathode surface and the arc voltage is constant for increasing gap length. In the axial magnetic field, the arc plasma was restricted within a column and the arc voltage rose with increasing gap length. When a magnet was arranged behind the anode, the arc plasma was constricted on the electrode axis and the lifetimes of the arcs became longer although the arc voltage rose with increasing gap length. The compression effect of the axial field was analyzed by introducing a simple magnetic piston model